Motor-generator system



C. L. KENNEDY.

MOTOR GENERATOR SYSTEM. APPLICATION HLED Oct. 23, 1916.

1,367,319. Patented Feb. 1, 1921.

2 4 6 Q) 7 SIGNAL TRANSMITTER /0 0 KEY 231 v Q5 25 22 /6 l7 RESISTANCEWar-Less I l ivefiio RATION OF MASSACHUSETTS.

a citizen of the United States, residing at South Braintree, in thecounty of Norfolk .and State of l\lassachusetts, have invented.

certain new and useful Improvements in Motor-(ienerator Systems; and Ido hereby declare the following to be a full, clear, and exactdescription of the invention. such as will enable others skilled in theart to which it appertains to make and use the same.

This invention relates to means for controlling the starting of anelectric motor. It is especially applicable to an electric system inwhich the motor constitutes an elementot a motor-generator, and in whichthe motor is loaded and unloaded by the closing and opening of thegenerator-circuit. In its wbroadest aspects, however, the invention isnot limited to use in this particular arrangement.

The object of the invention is to provide automatic means, of asimpleand reliable character, for preventing the subjection of themotor, during the starting thereof, to an excessive flow of current. Tothis end a starting-resistance is provided, in connection with anautomatic control]ing-device which prevents the operator of the motorfrom cutting out the resistance so long as the current flowing'in themotor exceeds a certain amount and the'speed of the motor issubstantially below normal. As a further means to'the same end, anautomatic device is provided for preventing the loading of the motorduring the startlug-operation, and in the specific form of the inventionemployed'in connection with a motor-generator, this device is arrangedto prevent closure of the load-circuit of the generator while themotor-speed is below normal and the current flowing in the motor isabove a predetermined amount.

Other objects of the invention, and the means by which they areattained, will be set forth in connection with the following descriptionof the preferred embodiment of the invention.

The accompanying drawing is a diagram of an electric system embodyingthe present invention.

The invention is illustrated as embodied 'in an electric system in whicha motor-generator is employed as the source of alter- Specification ofLetters Patent.

UNITED STATES PATENT, OFFICE.

- CARLTON L.- KENNEDY, OF SOUTH BRAINTREE, MASSACHUSETTS, ASSIGNOR TOTHE HOLTZER-CABOT ELECTRIC COMPANY, OF ROXBURY. MASSACHUSETTS, A CORPO-MOTOR-GENERATOR SYSTEM.

Patented Feb. 1, 1921.

Application filed October 23. 1916. Serial No. -1117,1771

nating current for energizing a signal-transmitter of a pulsatory type,such, for example, as that used in sub-aqueous signaling. Themotor-generator comprises a motorarmature 1 and a generator-armature 2,and,

the motor-armature is energized by direct current from any suitablesource, such as the generator 3 shown in the diagram. Thesignal-transmitter 4 may be of any ordinary or suitable type, but in thepresent application of the lnvention it will be understood that thistransmitter is employed in a system in which it is important that theperiodicity of the electrical pulsations be closely regulated.

The tield-wiiulings of the motor may be arranged in any manner known tobe suit- I able in such apparatus, and they are illus-' trateddiagrammatically as comprising a series-winding 5 and a shunt-winding 6,while the generator is provided with the usual shunt field-winding 7.The current from the source 3 is conducted through leads 8 and 9, andfrom the lead 8 the current passes, through the series field-winding 5and the motor-armature 1, to a wire 10 which is connected, through awire 11, with a resistance-device 12. From this resistancedevice thecurrent returns, through a wire 43 and the lead 9, to the source ofcurrent.

The resistancedevice 12 is employed both as a starting-resistance forthe motor, to prevent an excessive flow of current in the motor when it.is being started from a condition of rest, and as a regulatingresistance, to counteract the tendency of the motor to change its speedof operation when loaded and unloaded by the opening and closing of theload-circuit of the generator.

In order that the resistance may be em"- ployed for these functions,means are pro-- connected, by a wire 17, with the signaltransmitter,while the current returns from the latter to another brush of thegenerator, through the wire 18. A contact-plate 19 is carried by, butinsulated from, the relayarmature, and when the armature is raised thisplate engages the contacts and 16 and closes the load-circuit. At thesame time the armature closes the short-circuit above referred to. Thisis accomplished by the engagement of the armature with a fixed contact20, which is connected with the wire 10. by a wire 21. \Vlien thisengagement I occurs the current returning from the motorarmature flowsthrough the wires 10 and 21, and through the contact 20 and the armature13, and thence through the lead 9, which is connected with the armatureback to the source 3. A path of lowresistance is thus provided, whichrenders the resistance-device 12 ineffective.

The armature 13 is actuated by an electromagnet 22 controlled by a key23. This key constitutes the transmitting-key by which thesignal-transmitter is controlled. \Vhen the key is closed current flows,from the lead 8, t-hroughthe wire 24 to the key, and from the keythrough a wire 25 to the magnet 22. From the magnet the current returns,through a wire 26, to the wire 10 and thence, through the wire 11, theresistance-device 12 and the wires 43 and 9 back to the source 3.

During the normal operation of the apparatus the closing of the key 23at once results in the lifting of the relay-armature, so thatsimultaneously the load-circuit of the generator is closed and theresistance device 12 is short-circuited. This resistance-device is soproportioned as to compensate approximately for the load imposed uponthe motor-generator. Accordingly, the current flowing through thearmature of the genera- -tor is augmented sufficiently to meet the load,and thus is prevented the momentary drop in the speed of themotor-generator which would otherwise occur.

The apparatus as so far described is adapted only for operation at thenormal speed of the motor-generator, and the present invention residesparticularly in the employment of additional apparatus which will now bedescribed. A switch 31- is shown as interposed in the lead 8, thisswitch being that which is employed for the purpose of vention thisaction is automatically preventt ed, and as the referred means for thispun-- pose a second e ectromagnet 27 is shown, this magnet beingarranged to oppose the mag;- net 22, that is to say, it tends to holdthe relay-armature in its depressed positiom. The magnet 27 isconnected, by a wire 233 with the wire 11, and by a wire 29 with thewire 43, so that the magnet is connected; iiu parallel with theresistance-device andin series with the motor.

When the motor is starting, and is still running substantially belownormal speedt. there is a comparatively heavy current through the motor,and the difference in po' tential between the terminals of the resistiance-device 12 is comparatively great, and? the magnet 27 is stronglyenergized. At tiller same time the energization of the magnet 22' iscomparatively weak, owing to the fanti that this magnet is in parallelwith the motor and in series with the resistance-device and the magnet27. Accordingly, at tilliis time the magnet 22 in incapable of overconrr' ing the opposition of the magnet 27 and raising the relay-armature,and thus the resist ance-device is maintained in effective opera--tion'notwithstanding the depression of' thekey 23. When the motor-speedhas approx-i mately reached its normal rate, however, thus increasingthe counter E. M. F. of the motor and reducing the flow of current in:the motor, the flow through the magnet 2'7 is reduced, while the flowthrough the magenet 22 is increased, and the latter magnett will thenact to raise the armature 13 if the key 23 is closed, in accordance withthe non-- mal operation of the apparatus.

The magnet 27, by opposing the action on the magnet 22 during thestarting-operationz. not only prevents the short-circuiting of theresistance-device 12, but also prevent-ethicclosing of the load-circuitof the generatoir. It thus affords a further protection to tilhc motorduring the starting-operation, sinceit insures that the rapid rise ofthe motor speed to normal shall not be impeded by tl'nr imposition of aload on the motor. In the case of acomparatively small motor this formof protection alone may be sufficientt. since an unloaded motor, evenwhen subjectied to the full E. M. F. by which it is non mally operated,may attain normal speetlt and thus cut down the flow of current in themotor, with snfiicient promptness to prevonti injury to the motor fromthe momentamllw excessive current.

nor;-

"While the circuit closer comprising the armature 13 is shown anddescribed as in the form of a relay controlled indirectly by the key 23,it will be apparent that this arrangement is not an essential feature ofthe invention- It will also be apparent that the 1 two electromagneticwindings which oppose each 1 other in controlling the relay-arma- Thewinding of the: magnet 27, mally in series with .the motor,short-circuited. when the relay-armature 13 rises, acts in the samemanner as the resistance-device 12 to regulate the flow of currentwindin slight egree when the transmitting-key 23 .tion, amotor-generator; a 109.

forme The field-winding 7 of the generator is in'the motor. Accordingly,it may be possible in some arrangements to omit the re sistance-device12 and employ the magnet wmdm to perform the functions ,per'

by this resistance.

shown as connected with the current-lead 8 through a rheostat 30, bywhich the strength of the field may be adjusted to regulate the outputof the generator. The return from the field-winding 7 is either throughthe resistance-device 12 or through the shortcircuit provided by therelay-armature, and accordingly the flow of current throu h this isautomatically augments to a is closed. This arrangement has been foundto contribute to uniformity in the operation of the generator.

, The invention is not limited to the embodiment thereof hereinbeforedescribed and illustrated in the accompanying drawing, but may beembodied in various other forms within the scope of the followingclaims.

' The. invention claimed is:-

1. An electric system having, in combination, .a motor; means forloading and unloadm the motor; and means for automatica ly preventin theapplication of the load to the motorjw ile lt'lS running below apredetermined speed, I A a.

. 2. An electric system combin-ation, a motor; means for loadingandunloading the motor; and means for automatically preventin theapplicationof the load to the motor waile the current-flow in the motoris above a predetermined amount.

'3. Anelectric system having(i in combinanected with the'generator;means for closing the load-circuit; and means for automaticallypreventing theoperation of said means when the motor is runningsubstantially below a predetermined speed.

2 electric system having, in combination, a' motor-generator;' aload-circuit con-.

Y nected with the generator; means for clos- 66 ing the load-circuit;and means for auto- -circuit con matically preventing the operation ofsaid means "when the current-flow through the motor exceeds apredetermined amount.

5. An electric system having, in combination, anelectricmotor-generator; a load-circuit connected with the generator; acircuitcloser. controlling the load-circuit; and an anelectromagnetic'device, ener ized by the current flowing in the motor,or preventing the operation of the circuit-closer short-circuit; and anelectromagnetic de- 1 vice, connected across the terminals of theresistance-device for preventing operation of the circuit-closer.

7. An electric system having, 1n comb1nation, a motor having apredetermined nor- 'mal speed of operation; means for loadlng andunloading the motor; and automatic means responsive to the operatingconditions of said motor for permitting said means to load said motoronly when said motor operates at said normal speed.

8'. An electric system having, in combi nation, a motor-generator havinga predetermined normal speed of operation, and means dependent upon theoperatmg condn tions of said motor for closing; a load-circuit upon thegenerator only w en said motor o erates at said norm 1 speed..-

9. n electric system having, in combination, a motor-generator, meansfor starting the motor andbringing it-up to normal s eed; means forclosing a load-circuit upon t e generator; and automatic means forpreventmg the operation of said last means during the starting operationofthe motor.

10. An electric system having, in" combination, a motor-generator; astartmg and regulating resistance in circuit with the motor, means forexcluding said resistance from circuit;.means for closing a load-circuiton w the generator, and means for preventing the load circuit; means forconcurrently closing said load-circuit upon the generator an excludingsaid resistance from the motor circuit, whereby the speed of themotorgeneratorv is maintained constant; and means cooperating w th saidlast means and responslve to operatmg conditions of said motor forpreventing the operation of said .circuit; a circuit-closer forconnecting said load circuit to the generator, and an electromagneticdevice for operating said circuitcloser only when the motor is runningat normal speed, said device comprising opposing w ndihgs respectivelyresponsive to the counter-electro-motive force of the motor-and to thearmature current thereof. 13. An electric system having, in combination,a motor, a motor circuit, a speed regulating'resistance .in the motorarmature circuit, means for loading the motor, :and :means for excludingthe speed regulating resistance from the motor armature circuitconcurrently with the application of the load to the motor whereby adrop in the motor speed on application of the load is prevented.

14. An electric system having, in combi- ;-nation, a motor, a motorcircuit, a speed.

regulating resistance in the motor armaiture c1rcu1t, means for loadingthe motor,

\and means for automatically excluding the speed regulating resistancefrom the motor armature circuit concurrently with the application of theload to the motor whereby a drop in the motor speed on application ofthe load is revented.

1,5,An e ectric system having, in combimatlon, a motor generator, amotor circuit, ;a speed re lating resistance in the motor armatureclrcuit, means for up lying a load to the generator,.and means orexcluding the resistance from the motor armature circuit concurrentlywith the application of the load to the enerator whereby a dro in themotor s ee is prevente 16. An electric system having, in combination,amotor generator, a motor circuit, a speed regulating resistance in themotor armature circuit, means for concurrently applying a load to thetgenerator and for excludlng the resistance rom the motor armatureclrcuit whereby a drop in the motor speed on application of the load isprevented.

17. An electric system having, in combination, a motor generator, amotor circuit, a speed regulating resistance in the motor armaturec1'rcuit, a loadcircuit for the gen erator and a circuit closerforconnecting said load circuit=to the generator, said circuit closerhaving provision for excluding the speed regulating resistance from themotor armature circuit concurrently with the application of the load tothe generator whereby a dro in the motor speed on application of theload is prevented.

18. An electric system having, in combination, a motor, a motor circuit,a'speed regulating resistance in the motor circuit, means for loadingthe motor, means for excluding the speed regulating resistance from themotor circuit concurrently with the application of the load to the motorwhereby the motor speed is maintained constant, and means responsive to.the operating conditions of the motor for preventing the operation ofthe said last means during the starting of the motor. I

. OARLfrON L. KENNEDY.

on application of the oad.,

